Statistics from the China Giant Panda Breeding Technology Committee show that since the first panda cub was born in Beijing Zoo in 1963, most panda cubs born in captivity weigh between 83 and 190 grams. A 51-gram cub is very rare.

China began to artificially inseminate giant pandas in the 1960s but very few successful cases were reported.

Major breakthroughs began in the 1990s. Artificial insemination produced nine baby pandas in 2000, 12 in 2001, 10 in 2002 and 15 in 2003. The number rose to 25 last year, among which 21 survived.

Giant pandas show little instinctive behavior in captivity, especially sexual desire.

Forestry authority statistics show fewer than 10 percent of male giant pandas mate naturally and fewer than 30 percent of females conceive naturally.

Female pandas normally become sexually mature at age four or five and have only one chance of pregnancy a year. After a gestation period of about 160 days they deliver one or two cubs.

Studies from the State Forestry Administration show there are over 180 giant pandas living in captivity on the Chinese mainland.

Experts had previously estimated there were 1,590 giant pandas living in the wild in China, but Chinese and British scientists announced in June that there could be as many as 3,000 after a survey using a new method to profile DNA from giant panda feces.

The Chengdu center now has 48 adult giant pandas.